Conventional rectangular balers have a density control system which is typically done by regulating the pressure in the density belt. In such embodiments the pressure (and thus the force) on the bale chamber doors is controlled. In a typical conventional embodiment two hydraulic cylinders are used as actuators for controlling the top door and the side doors, respectively. The relation between the pressure exerted on the top doors and the side doors may be more or less fixed, wherein a system of balancing levers may be used to split the forces over the side and top doors.
In conventional balers, when the density has to be increased, the pressure in the density control system will be increased. In a particular embodiment, the compression ratio may be controlled by the density control system. The position of the doors results out of the crop parameters and the internal force ratio between the doors that is typically fixed in the construction.